5.5.2.11 Arithmetic Functions

The C arithmetic functions below always takes two arguments, while the
Scheme functions can take an arbitrary number. When you need to
invoke them with just one argument, for example to compute the
equivalent od (- x), pass SCM_UNDEFINED as the second
one: scm_difference (x, SCM_UNDEFINED).

— Scheme Procedure: + z1 ...
— C Function: scm_sum (z1, z2)

Return the sum of all parameter values. Return 0 if called without any
parameters.

— Scheme Procedure: - z1 z2 ...
— C Function: scm_difference (z1, z2)

If called with one argument z1, -z1 is returned. Otherwise
the sum of all but the first argument are subtracted from the first
argument.

— Scheme Procedure: * z1 ...
— C Function: scm_product (z1, z2)

Return the product of all arguments. If called without arguments, 1 is
returned.

— Scheme Procedure: / z1 z2 ...
— C Function: scm_divide (z1, z2)

Divide the first argument by the product of the remaining arguments. If
called with one argument z1, 1/z1 is returned.

— Scheme Procedure: 1+ z
— C Function: scm_oneplus (z)

Return z + 1.

— Scheme Procedure: 1- z
— C function: scm_oneminus (z)

Return z - 1.

— Scheme Procedure: abs x
— C Function: scm_abs (x)

Return the absolute value of x.

x must be a number with zero imaginary part. To calculate the
magnitude of a complex number, use magnitude instead.

— Scheme Procedure: max x1 x2 ...
— C Function: scm_max (x1, x2)

Return the maximum of all parameter values.

— Scheme Procedure: min x1 x2 ...
— C Function: scm_min (x1, x2)

Return the minimum of all parameter values.

— Scheme Procedure: truncate x
— C Function: scm_truncate_number (x)

Round the inexact number x towards zero.

— Scheme Procedure: round x
— C Function: scm_round_number (x)

Round the inexact number x to the nearest integer. When exactly
halfway between two integers, round to the even one.